1. Field of the Invention
The present invention relates to a smear preparing apparatus for preparing a smear of blood or bone marrow fluid collected. In further detail, the present invention relates to a smear preparing apparatus which allows easy preparation of a good-quality smear.
2. Description of Related Art
There has been used an apparatus for preparing a smear for observation purposes by dropping blood or the like onto a glass slide and spreading it with a spreader glass.
Since specimens are varied in properties such as particle density and viscosity, some of the specimens may result smears unsuitable for observation if the smearing conditions are fixed at any times.
For this reason, U.S. Pat. No. 5,209,903 discloses a smear preparing apparatus wherein the smearing conditions are established for each specimen based on the measurement results from a blood analyzer.
According to the prior art apparatus described above, the smearing conditions (the moving speed and the angle of the spreader glass) are changed automatically based on the analysis results of the blood analyzer. For example, it is commonly known that the smearing conditions are determined based on a hematocrit value. It is also considered that the smearing conditions are set on the basis of the number of leukocytes. Further, in consideration that the viscosity of blood generally increases in proportion to an increase in hemoglobin amount, it is also possible to establish the smearing conditions based on the measurement results of the hemoglobin amount by the blood analyzer.
However, in some cases, appropriate smearing conditions are not established by the method of automatically changing the smearing conditions depending on the hematocrit value. For example, the hematocrit value of a specimen collected from a leukemia patient is in the normal range or relatively small. However, since leukocytes of the leukemia patient are fragile and apt to be destroyed, the leukocytes may be broken under the smearing conditions established solely depending on the hematocrit value. Therefore, an appropriate smear cannot be prepared in some cases.
Upon preparing a blood smear of such a patient, it is necessary to reduce a force applied to the spreader glass which smears the blood on the glass slide such that the resulting blood smear has a relatively large thickness in which the leukocytes are not broken. However, in the prior art smear preparing apparatus, such adjustment has been difficult under the smearing conditions established depending on the measurement results of the analyzer.
In addition, persons who observe the smear with a microscope have various demands on the specimen. One observer wishes to observe a smear which is widely spread in a small thickness, while the other wishes to observe a smear which is concentrated in a small region with a large thickness. However, it has been difficult to meet such demands by the prior art smear preparing apparatus.